1. Field of the Invention
The present invention relates to valves for use in pumps handling abrasive laden fluids and, more particularly, to valve elements for use in piston pumps utilized in drilling and servicing of oil wells.
2. Description of the Background
In piston-type pumps such as triplex pumps which are used to pump drilling mud and other such abrasive laden fluids, a poppet valve comprised of a generally vertically disposed valve element and a valve seat is used to control the flow of fluid between an intake chamber and a discharge chamber. The valve element is biased, e.g. spring loaded, in the closed position. The action of the pump piston creates a suction in the discharge chamber forcing the valve element to open communication between the intake and discharge chamber, the valve element moving against the force of the spring. On the return stroke of the piston, the valve element, urged by the spring, moves down to engage the valve seat to seal off communication between the intake and the discharge chambers.
In pumps of the type under consideration, the valve element has an annular sealing surface which seals against a generally complimentary shaped seating surface provided by a valve seat disposed in the pump. Typically, the valve elements are provided with upper and lower guides in an attempt to ensure that the valve element stays aligned properly so as to allow the sealing surface on the valve element and the seating surface to properly mate when the valve element moves to the closed position. Thus, the valve element will have a central body portion which carries an annularly extending seat, the upper and lower guides projecting in opposite directions from the body portion.
Inherently, the structure of the valve element results in a high center of gravity. Accordingly, when the valve elements are moving from the open to the closed position, they have a tendency to tip or tilt off the true center line. This tendency to tip off center increases as the guides wear allowing more wobble of the valve element about the center line. Accordingly, rather than the sealing surface on the valve element engaging the seating surface at all points around its periphery substantially simultaneously, an area or a zone of the sealing surface strikes the seating surface first producing concentrated loading in this area as well as on a zone generally 180.degree. opposite this area as the valve element rocks or bounces around until it seals around the full periphery.
Valve elements for use in pumps of the type under consideration are known wherein a resilient sealing insert is bonded or otherwise secured to a generally metallic valve element structure. However, in such valve elements, both the upper and lower guides as well as the generally centrally located body portion are metallic in nature, the upper and lower guides and the body portion generally forming a monolithic structure. Along with making the valve element top heavy with a high center of gravity, this construction increases the overall weight of the valve element.